Bluetooth is a new technology which was developed as a short-range (about 10 meters) wireless cable replacement for linking portable consumer electronic products, such as cell phones, headsets, PDAs and laptop computers, but it can also be adapted for fax machines, printers, toys, digital cameras, household appliances and virtually any other digital consumer product or application. The technology essentially provides a mechanism for forming small wireless networks between Bluetooth-equipped devices on an ad hoc basis. It can also serve as a wireless communication bridge to existing data networks. Present Bluetooth implementation efforts generally focus on point-to-point client-server applications, such as, for example, the dialup networking profile, headset profile and local area network (LAN) access point profile (Bluetooth specification version 1.0). In these conventional implementations, Bluetooth-enabled devices will automatically seek each other out and configure themselves into networks, most often consisting of only two nodes.
Under a current specification (e.g., IEEE 802.15 Personal Area Network (PAN) developed by the PAN Working Group), up to eight Bluetooth-enabled devices can automatically configure themselves into a “piconet.” Each piconet has a designated master which imposes a frequency-hopping pattern on the rest of the nodes or devices functioning as slaves. A piconet is distinguished from other similar nets in the near vicinity by its unique frequency-hopping sequence. Since each piconet employs a different frequency-hopping sequence, multiple piconets can coexist in a common area.
Piconets can also be interconnected via bridge nodes to form a larger ad hoc network known as a scatternet (multiple independent and non-synchronized piconets). Bridge nodes are generally capable of timesharing between multiple piconets, receiving data from one piconet and forwarding it to another. There is essentially no restriction on the role a bridge node may play in each piconet it participates in. For example, a bridge can function as a master in one piconet and a slave in another, or it can be a slave in all participating piconets. In this manner, several piconets can be established and linked together in ad hoc scatternets to support flexible communication among continually changing configurations.
The Bluetooth baseband specification, as set forth in J. Haartsen, “Bluetooth Baseband Specification,” Version 1.0, which is incorporated herein by reference, defines the Bluetooth point-to-point connection establishment as a two step procedure. When Bluetooth units do not have any knowledge about their neighbors they must initially perform an inquiry procedure in order to discover the neighborhood information (e.g., node identities and synchronization information). Once the neighborhood information is available, a paging procedure is subsequently employed in order to establish the actual connection between the peers.
The inquiry and paging procedures comprise an asymmetric link establishment protocol which includes essentially two types of units:                Inquiring units, which try to discover and connect to neighbor units; and        Inquired units, which render themselves available to be discovered and connected with inquiring units.        
The Bluetooth baseband layer supports the following fundamental states for neighborhood discovery and connection establishment:                Inquiry: The Inquiry state is used to determine the identity of Bluetooth devices within a certain operating range. The discovering unit or device collects Bluetooth device addresses and clocks of all units that respond to the inquiry message.        Inquiry Scan: In this state, the Bluetooth devices are listening for inquiries from other devices. The scanning device may listen for a general inquiry access code (GIAC) or dedicated inquiry access codes (DIAC).        Page: This state is used by an inquiring device or unit that has discovered other devices through the inquiry procedure. The inquiring unit sends page messages by transmitting the inquired unit's device access code (DAC) in different hop channels.        Page Scan: In this state, a unit listens for its own device access code (DAC) for a duration of scan window. The unit listens at a single hop frequency (derived from its page-hopping sequence) in this scan window.        Connection: As soon as this state is established, one unit is the master and the other is the slave. In this state the units can exchange packets using the channel-hopping sequence that is determined by the channel (master) access code and the master Bluetooth clock.        Standby: Standby is a default low power state in the Bluetooth unit. Only the native clock is running and there is no interaction with any other device.        
There are also several intermediate states, namely, Inquiry Response, Slave Response and Master Response. These states will be described in further detail in connection with a description of the Bluetooth connection establishment protocol that follows.
FIG. 1 illustrates a logical flow diagram 100 showing a conventional point-to-point connection establishment procedure between two Bluetooth-enabled devices, namely, an Inquiring Unit 101 and an Inquired Unit 102. Both units use a universal frequency-hopping set called an inquiry hopping sequence. The steps involved in the standard connection establishment process are as follows:                1. The inquiring unit 101 first enters the INQUIRY state 120 and tries to discover which devices are within range by rapidly transmitting an Inquiry Access Code (IAC) packet 111 at a rate of 3200 hops/second, according to the universal inquiry hopping sequence, and listening for an answer between transmissions.        2. The inquired unit 102 starts in the INQUIRY SCAN state 130 and thus renders itself available to be discovered by nearby inquiring units. The inquired unit 102 starts listening on a frequency carrier for a possible inquiring unit 101 transmitting an inquiry message on this specific frequency. Every 1.28 seconds, the unit moves its listening carrier forward one hop (in frequency channel) according to the universal inquiry hopping sequence. It is evident that there is an associated frequency synchronization delay until the inquiring unit 101 and the inquired unit 102 synch to the same frequency channel.        3. Once the inquiring unit 101 and the inquired unit 102 are communicating on the same frequency, the inquired device 102 receives IAC packet 111 from the inquiring unit 101. Upon reception of the inquiry message, the inquired unit 102 goes to the STANDBY state 140 and “sleeps” for a predetermined time, R, uniformly distributed between 0 and 639 milliseconds.        4. Inquired unit 102 subsequently wakes up and begins listening again in the INQUIRY RESPONSE state 150 by starting frequency-hopping from the hop it was listening to before sleeping.        5. A second IAC packet 112 is received and the inquired unit 102 returns a frequency-hopping sequence (FHS) packet 113 to the inquiring unit 101. The FHS packet 113 contains the inquired unit's Bluetooth address and clock value, which is considered valuable synchronization information to the inquiring unit 101, that speeds up the paging process that will follow. Immediately after responding with a FHS packet 113, inquired unit 102 enters the PAGE SCAN state 160 and starts listening for its own Device Access Code (DAC) by hopping according to its own page hopping sequence.        6. On the Inquiring unit side, inquiring unit 101 receives the FHS packet 113 from the inquired unit 102 along with information that is used to determine the DAC and page hopping sequence of inquired unit 102. From this point, the paging procedure is initiated. Inquiring unit 101 enters the PAGE state 170 and starts paging by sending the DAC packet 114 according to inquired unit's 102 page hopping sequence.        7. Inquired unit 102 receives DAC packet 114, subsequently responds by transmitting DAC packet 115 and enters the SLAVE RESPONSE substate 180.        8. Inquiring unit 101 receives DAC packet 115 sent by the inquired unit 102, enters the MASTER RESPONSE substate 190 and then sends a FHS packet 116 to the inquired unit 102 containing its address and clock information.        9. Inquired unit 102 receives FHS packet 116 transmitted by the inquiring unit 101 and changes to the inquiring unit's 101 channel access code and clock, as received in the FHS packet 116. Inquired unit 102 then sends DAC packet 117 as an acknowledgment to the receipt of FHS packet 116 and subsequently enters the CONNECTION state 198 having the role of the slave in this point-to-point connection.        10. Inquiring unit 101, upon receiving DAC packet 117 from the inquired unit 102, enters CONNECTION state 199 and becomes the master of the point-to-point connection.        
In accordance with the conventional Bluetooth protocol set forth above, the connection between two Bluetooth-enabled devices can be established and the devices can subsequently exchange any desired amount of information.
Although Bluetooth is a promising new technology, there exist several disadvantages inherent in the conventional connection establishment procedure or protocol. As noted above, Bluetooth supports peer-to-peer, ad hoc wireless connectivity. That is, two devices in proximity can discover each other and form a communication link therebetween. Since Bluetooth utilizes frequency-hopping spread-spectrum technology to support point-to-point and point-to-multipoint connections, devices must synchronize their frequency-hopping patterns before they can communicate with one another. This implies that hosts are not able to communicate unless they have previously “discovered” each other by synchronizing their frequency-hopping patterns. Even if all nodes are within direct communication range of each other, random synchronization delays are introduced during the formation of individual links in the network. The process of synchronization (or Inquiry in Bluetooth terminology) is a time consuming as well as asymmetric (i.e., requiring two nodes to be in different initial states) process. Consequently, when two Bluetooth devices are powered on, it may take several seconds to establish a link between the devices.